A short history of hydrometallurgy

A short history of hydrometallurgy
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  See discussions, stats, and author profiles for this publication at: A short history of hydrometallurgy   Article   in  Hydrometallurgy · September 2005 DOI: 10.1016/j.hydromet.2004.01.008 CITATIONS 59 READS 1,383 1 author:Some of the authors of this publication are also working on these related projects: Writing books   View projectFathi HabashiLaval University 346   PUBLICATIONS   1,607   CITATIONS   SEE PROFILE All content following this page was uploaded by Fathi Habashi on 03 January 2017. The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the srcinal documentand are linked to publications on ResearchGate, letting you access and read them immediately.  A short history of hydrometallurgy Fathi Habashi  Department of Mining, Metallurgical, and Materials Engineering, Laval University, Quebec City, Canada G1K 7P4 Received 9 January 2003; received in revised form 19 December 2003; accepted 29 January 2004Available online 28 July 2005Dedicated to the memory of Vladimir N. Mackiw (1923–2001), a distinguished Canadian hydrometallurgist  Abstract Thousands of years ago people had learned how to build furnaces and use fire to melt rocks and produce metals but the useof aqueous solutions for ore processing came much later, mainly at the time of the alchemists when acids and alkalies becameknown and used. Modern hydrometallurgy, however, can be traced back to the end of the 19th century when two major operations were discovered: the cyanidation process for gold and silver extraction and the Bayer process for bauxite treatment.Later, in the 1940s, a breakthrough came during the Manhattan Project in USA in connection with uranium extraction. Sincethen, it has been advancing progressively and even replacing some pyrometallurgical processes. Canadian contribution issignificant particularly in the recovery of uranium, nickel, cobalt, and zinc. D  2005 Elsevier B.V. All rights reserved. 1. Introduction The roots of hydrometallurgy may be traced back to the period of alchemists when the transmutation of  base metals into gold was their prime occupation(Habashi, 1993a). Some of these operations involved wet, i.e., hydrometallurgical methods. For example,when an alchemist dipped a piece of iron into asolution of blue vitriol, i.e., copper sulfate, the ironwas immediately covered by a layer of metallic cop- per. This apparent transmutation of iron into copper isrepresented in modern terms by the equation:Cu 2+ +Fe Y Cu+Fe 2+ , but it was not known at that time that blue vitriol contained copper. The major question, however, that remained unanswered was:how can the transmutation of iron or copper intogold be effected? Gold, the most noble of all metalsdissolved in mercury forming an amalgam but wasinsoluble in all acids or alkalies known at that time.The discovery of aqua regia by Jabir Ibn Hayyan(720–813 AD) (Fig. 1), the Arab alchemist, may be considered as a milestone marking the beginning of hydrometallurgy. Aqua regia, i.e., royal water, is amixture of HCl and HNO 3  that dissolves gold; neither of the acids alone has any dissolving action. Aquaregia is still used today for gold refining, and chlorineone of its active ingredients: 3HCl+HNO 3 Y Cl 2 + NOCl+2H 2 O was utilized extensively for extractinggold from its ores till the 1890s. 0304-386X/$ - see front matter   D  2005 Elsevier B.V. All rights reserved.doi:10.1016/j.hydromet.2004.01.008  E-mail address: 79 (2005) 15–   In the Middle Ages, certain soils containing putre-fied organic matter were leached to extract saltpeter (=salt of stone, potassium nitrate), a necessary ingre-dient for the manufacture of gunpowder. The processwas fully described by Vannoccio Biringuccio (1480– 1539) in his  Pirotechnia  published in 1540.In the 16th century, the extraction of copper by wet methods received some attention. Heap leaching was practicedintheHarzmountainsareainGermanyandinRı´o Tinto mines in Spain. In these operations, pyritecontaining some copper sulfide minerals was piled intheopenairand left for months to the action of rain andair whereby oxidation and dissolution of copper took  place.Asolutioncontainingcoppersulfatewasdrainedfrom the heap and collected in a basin. Metallic copper wasthenprecipitated from thissolutionbyscrap iron,a process that became known as  b cementation process  Q  ,which is apparently derived from the Spanish b cementacio´n  Q   meaning precipitation. This is thesame process that was already known to the alchemistsand is still in operation today to an appreciable extent.In the 18th century, one of the most important industries in Quebec was the production of potashfor export to France to satisfy the needs of the soapand glass industries. Before the invention of theLeblanc Process for the manufacture of Na 2 CO 3 from NaCl, the main source of Na 2 CO 3  was fromashes of seashore vegetation, and that of potash wasfrom ashes produced by burning wood in areas wherethe clearing of forests was in progress on a large scale.The importance of this process to hydrometallurgylies in the fact that leaching was extensively practiced.During the period 1767–1867, wood ash was col-lected from domestic stoves and fireplaces, and fromlime kilns, then agitated with water, filtered, thenevaporated to dryness to yield potash. One ton potashrequired the burning of 400 tons of hardwood, whichis equivalent to the cutting of about 10 acres of forest. 2. The beginnings The birth of modern hydrometallurgy dates back to1887 when two important processes were invented.The first, the cyanidation process for treating goldores, and the second, the Bayer Process for the pro-duction of alumina. 2.1. Cyanidation process The dissolving action of cyanide solution on metal-lic gold was known as early as 1783 by the Swedishchemist Carl Wilhelm Scheele (Habashi, 1987). L. Elsner in Germany in 1846 studied this reaction andnoted that atmospheric oxygen played an important role during dissolution. The application of this knowl-edge to extract gold from its ores was proposed and patented much later in England by John Stewart MacArthur (1856–1920) (Fig. 2) in 1887 and became known as the cyanidation process. G. Bodla¨nder in1896 made the important discovery that hydrogen peroxide was formed as an intermediate product dur-ing the dissolution of gold. Fig. 1. The Arab alchemist Jabir Ibn Hayyan (720–813 AD), dis-coverer of   aqua regia  (royal water) for dissolving gold—the king of metals.Fig. 2. John Stewart MacArthur (1856–1920), discoverer of thecyanidation process.  F. Habashi / Hydrometallurgy 79 (2005) 15–22 16  The cyanidation process had already been applied toeach mining district in the world and still its chemistrywas very obscure. Its impact on hydrometallurgy had been tremendous. Extremely large reactors known asDorr agitators in which the finely ground ore wasagitated with the cyanide leaching agent and equippedwith compressed air injection in the pulp had beendesigned and built by the metallurgical engineer JohnDorr. Huge filtration plants designed to obtain clear leach solutions for metal recovery were similarly con-structed. The ancient process known as cementationwhich was applied only for precipitating copper fromsolution by scrap iron was applied to gold solutions,iron being replaced by zinc. In spite of all theseadvances in engineering and the wide application of the process, the theory still remained lagging behind.As a result of introducing the cyanidation processworldwide, gold production increased greatly duringthe period 1900–1910 (Fig. 3). 2.2. Bayer process The second major hydrometallurgical process of this era was the process invented by Karl Josef Bayer (1847–1904) (Fig. 4) for the preparation of   pure Al 2 O 3  and known as the  Bayer Process  (Haba-shi, 1995). This process was concerned with leaching bauxite, discovered in 1821 in France in a smallvillage called Les Baux, near Marseille, with sodiumhydroxide solution above its boiling point in a pres-sure reactor. After separating the insoluble material,the pure solution was then seeded to precipitate purecrystalline aluminum hydroxide which was filtered,washed, dried, and calcined to pure Al 2 O 3  suitable for charging to the electrolytic reduction cell invented 2years earlier. Bayer was an Austrian chemist workingin Saint Petersburg, in Russia; his process is used at  present in its srcinal version with practically nochange. It is interesting to point out the following: !  The process was srcinally developed to satisfy theneeds of the textile industry since aluminum hydro-xide was used as a mordant in dyeing cotton. It wasonly after the invention of the electrolytic alumi-num process in 1886 that the process gained impor-tance in metallurgy. !  Bayer’s first contribution was in 1887 when hediscovered that Al(OH) 3  precipitated from alkalinesolution was  crystalline , easy to filter, and washfree from impurities while that precipitated fromacid medium by neutralization was gelatinous anddifficult to filter and wash. !  A few years earlier to Bayer’s invention, Louis LeChatelier (1815–1873) in France described amethod for making Al 2 O 3  by heating bauxitewith Na 2 CO 3  at 1200  8 C, leaching the sodiumaluminate formed with water, then precipitating Fig. 3. Increase in world gold and silver production between 1900and 1910 as a result of introducing the cyanidation process.Fig. 4. Karl Josef Bayer (1847–1904), inventor of the process for the production of alumina from bauxite.  F. Habashi / Hydrometallurgy 79 (2005) 15–22  17  Al(OH) 3  by CO 2  which was then filtered, dried,and claimed to pure Al 2 O 3 . This process wasabandoned in favor of the Bayer process (Fig. 5). 3. Further development At the beginning of the 20th century numerousleaching and recovery processes were proposed,some of them were put into practice, others had towait for about half a century until they were applied,while others never developed beyond a pilot plant.When examining the patent literature at the begin-ning of this century it is remarkable to see the largevariety of leaching agents proposed. In 1903, M.Malzac in France proposed the use of ammoniasolutions for leaching sulfides of copper, nickel,and cobalt. At that time NH 3  was an expensivereagent obtained exclusively as a by-product of thecoal industry. It became a cheap commercial reagent only after its synthesis 10 years later by Fritz Haber in Germany. Nitric acid was proposed by Kingsley in1909 for leaching sulfide ores. Also, at that timeHNO 3  was an expensive reagent obtained exclusivelyfrom the sodium nitrate deposits in Chile by treat-ment with concentrated H 2 SO 4 . It became relativelycheap only after the invention of Haber’s processsince nitric acid is made now exclusively by theoxidation of ammonia.Towards the beginning of the 20th century, hydro-metallurgy of copper received a particular attention.Oxide ores were leached on large scale by dilutesulfuric acid in Chile. Copper sulfides were alsosolubilized due to the presence of ferric ion whichacted as an oxidizing agent. Instead of precipitatingcopper from leach solution by scrap iron in the usualway, electrowinning was used in Chile in 1912 (Haba-shi, 1998). The First World War (1914–1918) createda demand for the zinc for the manufacture of cartridge brass. Zinc for this purpose used to be obtained by thedistillation of commercially available metal in Bel-gium and Germany from ore supplied by Australia.This situation inspired industry in North America tosupply additional metal from ores that were not amen-able to standard methods. At Trail in British Columbiaand Anaconda in Montana, the processes for electro-lytic zinc and the leaching of a large tonnage of ZnO by H 2 SO 4  was introduced. The process is mainly SINTERINGNa 2 CO 3  Na 2 CO 3 bauxite bauxiteNaOHwater waterresidue residueseedLEACHINGFILTRATIONCO 2 PRECIPITATIONFILTRATIONEVAPORATIONTO DRYNESSSINTERINGLEACHING LEACHINGPRESSUREFILTRATION FILTRATIONFILTRATIONseedbauxiteresiduePRECIPITATION PRECIPITATIONFILTRATIONEVAPORATION EVAPORATIONTO DRYNESS LE CHATELIER BAYER1855 1888BAYER1892 solution solution solutionAI (OH) 3  AI (OH) 3  AI (OH) 3 Fig. 5. Bayer process displaced Le Chatelier pyrometallurgical route.  F. Habashi / Hydrometallurgy 79 (2005) 15–22 18
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